For hygiene monitoring on surfaces RIDA®COUNT Salmonella/Enterobacteriaceae test cards can be directly applied to the surface to detect and quantify Salmonella or total Enterobacteria.

RIDA®COUNTs are non-woven membrane culture medium sheets presented in a ready to use test card format. The card is multi-layered, built up from a base followed by a nutrient layer and topped with a layer of inert polymer to absorb the test liquid. A non-woven fabric layer makes up The final top surface is a non-woven fabric layer which ensures the structural stability of the test card. Counting the developing colonies is made easier by a plastic foil covering that has an integrated counting grid.

The detection technique of RIDA®COUNT Salmonella/Enterobacteriaceae test cards is based on modified VRB (Violet Red Bile) medium containing the chromogenic substances X-alpha-Gal and Salmon-beta-Gal.

Bile salts inhibit Gram-positive bacteria. The substrate X-alpha-Gal is reduced by alpha-galactosidase an enzyme specific for Salmonella. The substrate Salmon-beta-Gal is reduced by beta-galactosidase which is not produced by Salmonella though is present in the majority of Enterobacteriaceae. The formation of blue colonies on the test card typically shows Salmonella colonies while all other colours from magenta to purple or indigo indicate the presence of other Enterobacteriaceae.